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“Everything should be made as simple as possible, but not simpler.”, A. Einstein.

It is a “scientific” creed similar to Occam’s razor summarized as, “The simplest explanation is usually correct.” These two guiding principles provide direction when you are looking for explanations and aren’t sure how to proceed. But, they also underpin a philosophy of design that creates unadorned, straightforward products that are a delight to experience.

My appreciation of BMW airhead motorcycles is a practical expression of Einstein’s prescription of what the result of science should look like. Airhead design is functional, not elaborate nor flamboyant. The styling relies on form following function for its appeal, not on plastic panels and extraneous amenities that distract from the direct understanding of how the machine works. Even when BMW introduced the first motorcycle with a manufacturer integrated full fairing in 1977, the R100RS, the shape of the fairing was defined by aerodynamic necessity and the requirement to protect the rider from adverse weather. I think the RS fairing is a design that solves several hard problems as simply as possible, but no simpler.

For BMW airheads, the art in the design lies in engineering control of material properties and precision machining during manufacture. For example, machined tapers with press fits are preferred to castle nuts with tab washers when connecting driven components on a turning shaft. Parts inventory is minimized and the assembly procedure is simple.

Another example is the tool kit that comes with the bike. With it, you can disassemble just about anything on the motorcycle. I’ve used the tool kit to remove the top end to replace rings and then reassemble it. I have removed the transmission, the drive shaft, the entire rear sub-frame and the rear wheel with it. Nothing else in my tool box was required. That lowly, hidden tool kit is an elegant expression of the minimalist mindset.

The joy of motorcycling comes from a direct, frictionless connection between mind and action, but that is deepened when the machine you are riding is an elegant execution of the minimalist creed espoused by Einstein.

I think that’s why I got so involved in airhead wrenching over the last decade.

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I put together a series of pages about BMW airhead motorcycle electrical systems. It strikes me that electricity in general, and motorcycle electrics in particular, are dark mysteries to many, so I thought I’d shine some light [puns intended 🙂 ].

Lack of understanding hinders confidence when diagnosing and working on electrical projects. As these bikes age, the electrical system is prone to problems as corrosion and neglect makes them behave badly. More owners are having more electrical problems but seem less able to get to the root cause of the problem.

I think one tool that many avoid using is the wiring diagram. The spaghetti of lines, symbols and notations makes the eyes glaze over. “Oh goodness, where do I start?” is the common response to the advice, “Look at the wiring diagram.”

I’m not an electrical engineer, but I have taken time to learn the basics, have collected comments and input from well respected airhead mechanics and dug into how BMW applied electrical theory when they designed the /5 electrical system. I’ve learned a lot from various reference sources that are scattered about the internet, so my articles include a bibliography of various useful resources. That way both you and I have a nice set of reference materials to consult when problems come up.

I have published three articles (so far), Basics and two about the /5 series: 5 Series Electrical Circuits and, 5 Series Electrical Components. I chose the /5 series to start with because I believe it’s the most popular airhead series for restoration.

I hope to write an Electrical Circuits and Electrical Components document for the /6 and /7 series up to 1984.

This is the most critical, precise piece of work I’ve taken on. Before doing this project, I did a lot of research. I had access to special tools, a shop press and advice from two local airhead mechanics. Without those resources, and spending a couple months trying to learn what I needed to know about this work, I wouldn’t have attempted to do it.

Despite all that, I managed to overlook a new, but wrong size, $2.95 circlip that holds the cam roller on it’s pin. It separated company from the pin about 2000 miles after I finished rebuilding the bike. I was in Indiana at the time on my way to the 40th RS rally in Pennsylvania. Mr. Cutter, who was attending the rally, stepped in and devoted a Sunday to save my bacon. Watching him do the work in a day I had labored over for weeks reinforced the value you get from someone who has spent 45 years making mistakes and learning from them so you don’t have to 🙂

So, in retrospect, I should say I relied on three airhead mechanics to do this work 😉

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In two months since I completed the build, I’ve ridden the bike 4,400 miles. I named it “Gonzo” as I like to name my bikes after Muppet characters :-).

Gonzo Starting Mileage On Departure for Pennsylvania

I rode it to the 40th R100RS anniversary rally in Pennsylvania and back and had a problem with the transmission about 350 miles from the rally that required me to stop riding until it was fixed. That work was done by Tom Cutter of Rubber Chicken Racing Garage and I completed the ride home only one day late.

I documented the issues, corrections and updates I made from the first engine start through the end of my ride back from Pennsylvania here.

Here are links to two set’s of pictures, the first are the ones I took on the trip and at the rally, and the second are by, Andy Muller, a photographer, who is the proud owner of the 40th RS sold in the US so of course he brought it to the 40th RS anniversary rally. What a nice bit of serendipity.

Getting There, Days 2 – 5

My route to the rally follows US 36 which passes through Hannibal, MO.

On the Way to the Rally

Hannibal Waterfront

Mississippi River, Hannibal MO

Mark Twain Statue at Hannibal Waterfront

I planned a shorter ride the day I arrived in Hannibal so I could spend some time visiting the Mark Twain museum. I stayed at a B&B in a 19th century home, the Dubach Inn. My suite was on the second floor with it’s own staircase and balcony where I enjoyed a Gin and Tonic at the end of the day.

Dubach Inn, Hannibal MO

The city turned the block where Twain grew up into a museum that includes his home, his father’s justice of the peace office, Becky Thacher’s house, and the home that was occasionally used by the street urchin he crafted Huckleberry Finn from. I really enjoyed the exhibits and learned a lot more about Twain’s life and the impact of it on his personality and ultimately how it became the source for many of the books that made him famous.

Reconstruction of Huck Finn House at Mark Twain Museum

Mark Twain Museum

Mark Twain Museum

Mark Twain Museum

Mark Twain Museum

Along US 36 I saw a number of signs about the pony express and the stops and routes they used. A rider would take the mail and ride a set distance each day and then hand the mail pouch to another rider who continued with the mail. The first rider then took mail from a rider coming the other direction and returned with it to where he started. This shuttling operation moved the mail from St Louis to California. Little did I know at the time that the Airhead Pony Express would be enlisted to deliver Gonzo and I on the last leg of the trip to the rally.

The next day I stop at a hotel in a suburb of Indianapolis, IN. At the start of the day I enjoyed riding on two lane roads although I was riding in a light rain and some fog for awhile. I took some state and county roads to avoid the heavy traffic I recall from a previous ride to the east coast on I-70 through Indianapolis. Alas, I poked along through Indianapolis suburban sprawl, construction zones for the last hour. It was a long day.

On the Way to the Rally

On the Way to the Rally

After I got to the hotel, I thought I heard noise from the transmission. I had replaced the bearings and seals, my first time doing this work, so I was worried I had failed to do the work correctly. But when I got up the next morning under a dull gray sky with light rain and drizzle and started the bike the transmission seemed to be quiet. I chalked up the noise I thought I heard to my paranoia and being hyper-sensitive to the new sounds from an unfamiliar bike and transmission.

I headed out in the drizzle and mist on my way to West Virginia near the Pennsylvania boarder to my next hotel. At my first gas stop late in the morning, I could hear the transmission noise again. It was louder and clearly something was not right. I still had another 200 miles to my hotel and no hope of finding any airhead transmission experts in this part of the country. At the end of the day I would still be about 350 miles from the rally location in Pennsylvania.

On the Way to the Rally

40th R100RS Anniversary Rally

Diagnosing the Problem

Tom Cutter, one of the best airhead mechanics and an expert transmission builder, was coming to the rally and he lives pretty close by. When I got to my hotel in Triadelphia WV I called him and described what I was hearing. I told him I planned to bring the bike to him and leave it and I would figure out how to get back home. He told me not to worry. He would start work on the bike on Sunday right after the rally and would get me back on the road as soon as possible. The huge weight of worry and dread that had been weighing on me all day suddenly vanished.

He had me do a number of tests including draining the transmission at an auto parts store to see what came out. When I got there and bought some gear lube and a drain pain, it was raining lightly and the light was fading as I started to drain the gear box in the parking lot.

Draining Transmission Oil at an Auto Zone in Triadelphia West Virginia

When I removed the drain plug, I found a circlip stuck to it. It secures the plastic roller that rides on the shift cam to a pin on the shifter arm. That can’t be good. I used my cell phone to send a picture to Tom. His advice was to not ride the bike any more if at all possible. I was tired, a bit wet and dejected as I rode Gonzo five miles back to the hotel in the dark to get something to eat.

Circlip from Shift Quadrant Roller – Shouldn’t Be In The Transmission 🙁

The Airhead Pony Express

After dinner I decided to post a note to the newsgroup used by rally members for communication to see if anyone might be in the area with a trailer that could take Gonzo and I to the rally hotel in Pennsylvania and then went to bed for a night of fitful sleep as I reviewed scenarios of how to get to the rally and all the changes I had to make to my return hotel reservations since I was going to be delayed. On top of that, my credit card had been fraudulently used on the internet and the card company had cancelled it. Ah, it never rains but it pours 🙂

The next morning, I saw a note from Duane Wilding who lives near Annapolis, MD. He offered to load his bike on his trailer instead of riding to the rally and it had room for mine. The detour would double the time for him to get to to rally changing a 5 hour day of riding to more like 10 or 11 hours of towing. I didn’t see any other offers so I called him and asked him to come pick me up. It would take him an hour and a half to get the trailer hooked up and and I agreed to call him if in the mean time I heard from someone closer who was able to help.

I started to call my hotels to put my rooms on hold, called my wife to let her know what was happening and as I scrolled through other email, I suddenly saw a reply posted by Scott Mercer right after I sent my note. I had missed it when I first looked at my Email. His note said he was an hour and a half away and had a truck with his bike in it and there was room to add mine. I connected with him, confirmed he was still able to come by and pick up Gonzo and told him I’d call him back as I had to cancel my ride from Duane who was going well out of his way to help.

When I called Duane back and told him to stand down, I reached him just before he was about to start driving my way. And then I got two more calls, one from Scott’s friend, Tom Gaiser, who was bringing his R90S in his pick up truck and said he would come by in case we needed help getting Gonzo in Scott’s truck. When I hung up I got a call from Keven O’Neil who was bringing his bike on a trailer following my route from Indianapolis. He too said he would stop to help and in case my bike didn’t fit in Scott’s truck, there was room on his trailer. I had gone from famine to feast. I was overwhelmed by the generosity and support from these Airheads. What a great bunch they are.

Airhead Pony Express Arrives

Mike Mercer’s Trailer with Tom Gaiser Supervising

Gonzo in Mike Mercer’s Trailer Next to His Mint 1978 Motosport

Five hours later we turned off the Pennsylvania Turnpike and stopped next to an appliance that was as ubiquitous as cell phones are today when the RS was brand new. I couldn’t resist; I went over, picked up the handset and it had a dial tone. That pay phone still works for it’s intended purpose, just as my 1977 RS does. How unexpected, and fitting to find this relic on my journey to a 40th R100RS anniversary rally.

Working Pay Phone at Our Exit on Pennsylvania Turnpike

We pulled into the Holiday Inn parking lot, unloaded Gonzo and parked him in the growing group of RS bikes in the parking lot. Then Scott and Tom drove to their hotel 20 minutes away.

The Rally at Todd Trumbore’s Home

The next morning, Friday, I got a ride to the rally at Todd Trumbore’s home where the rally was held from Mike Cecchini who brought his bike on a trailer.

Todd Trumbore Host for 40th R100RS Anniversary Rally

I spent the day in awe of the variety of bikes parked outside Todd’s “Bavarian Bike Barn” including a Munch Mammoth, an ISDT race bik, a replica of the Udo Gietl prepared R90S that won Daytona in 1976 and the first AMA Super Bike championship, A Mondial and of course, multiple examples of well cared for RS bikes and more first year bikes than I’ve ever seen in one place a one time.

Munch Mammoth

Here is a short video of starting the Mammoth and the sound it makes.

Some of the 40th RS Anniversary Rally Attendees and Their Bikes

ISDT Race Bike Restoration

ISDT Race Bike Restoration

ISDT Race Bike Restoration

Udo Gietl Prepared 1976 RS Race Bike Replica

Udo Gietl Prepared 1976 RS Race Bike Replica

Todd Trumbore’s Restored Mondial – Gorgeous

Todd Trumbore’s Restored Mondial – Gorgeous

300,000+ Mile Custom R90S

300,000+ Mile Custom R90S

300,000+ Mile Custom R90S – Interesting Spark Plug Wire 🙂

300,000+ Mile Custom R90S

There were talks by Hans Muth, Udo Gietl, and Tom Cutter, and numerous conversations with fellow airhead RS owners about their bikes. Hans graciously designed the logo on the far right and Todd did the other two. I have all three stickers from the rally and will find a suitable place of honor for them in my work shop.

40th RS Anniversary Rally Logo’s Designed by Hans Muth

Hans Muth

Udo Gietl

Tom Cutter

On Saturday, Mike put Gonzo in his trailer and as the next airhead pony express rider, faithfully delivered us to Todd Trumbore’s. We unloaded Gonzo and I rode him up Todd’s driveway so I could say with a straight face that I rode him to the rally. 🙂

Gonzo Getting Tied Down in Mike Cecchini’s Trailer

My 1977 RS – “Gonzo” – Parked Among His Fellow 1977 R100RS Bikes

Mike Cecchini’s R90S Fitted in RS Body Work – Beautiful !!!

Meeting Hans Muth and Getting Gonzo an Autograph

It took a year of work rebuilding the bike and several adventures along the way while riding him to Pennsylvania, but I met Hans Muth, shook his hand and got his autograph on Gonzo’s factory inspection sticker. An amazing end to a year of work and adventure riding to the rally.

Shaking Hands with Hans Muth Next To My 1977 R100RS

Hans A. Muth Signature on My 1977 R100RS Factory Inspection Sticker

Fixing Gonzo’s Transmission

Saturday evening, Tom Cutter and I loaded Gonzo on his trailer and I rode Tom’s “Fake S” R100/7 to his house that is about an hour away. What a treat, to say the least. 🙂

Gonzo Loaded in Tom Cutter’s Trailer Next to His R Nine T

Tom Cutter’s “Fake S” That He Let Me Ride – What a Hoot and Very Kind of Him

On Sunday, he pulled the transmission out, disassembled it, cleaned and inspected it, replace the circlip and roller, and reassembled it. He found no other damage to the transmission. After careful measurement of my circlip and a new one, it seems the new one I installed is not the correct size. I failed to catch that when I installed it since this was the first time I had opened a transmission so I had no experience with the parts. That said, in the future, I can compare the new parts to the old to reduce this kind of mistake in the future.

My Circlip (Left), Correct New One (Right)

the circlip was a bit too large compared to the new one he installed. Either it was a defective part, or I damaged it when I installed it. On Monday morning, we installed Gonzo’s transmission and Tom took care of a couple other assembly mistakes I made. By 2:00 pm Monday, I was back on the road heading home.

Going Back Home

I rode on US 50 most of the way until Topeka Kansas where I got on I-70. I went through Athens, Ohio on Tuesday and stopped to meet Kent Holt of Holt BMW who provided the paint and a great deal of advice when I tried my hand at painting. He took me on a tour of his facility and he spent almost two hours talking with me. What a treat/.

Marvin Greeted Me at Holt BMW with Coffee 🙂

Kent Holt in his Work Shop

Kent Holt’s Ride with Custom Paint Work

I stopped in Jefferson City, MO to stay at a B&B housed in a civil war ear home built on a high bluff over looking the Missouri River and had dinner at an Irish pub around that corner, Paddy Malone’s, that is one of the oldest continuously operating pubs in the mid-west. There is a flag from every county in Ireland on the ceilings and walls. A great place to relax.

Cliff Manor B&B Jefferson City MO

Gonzo Resting at the Cliff Manor B&B Jefferson City MO

Missouri River From Patio of Cliff Manor B&B Jefferson City MO

Beer Board at Paddy Malone’s Pub in Jefferson City MO

Jefferson City MO Irish Pub with County Flags

The next day I rode to Hays, Kansas. In the afternoon, I had 30 MPH cross winds for several hours and at one point, the bike thermometer showed 102 F. The air conditioned lobby of the hotel was very refreshing 🙂

I arrived home on Friday about noon after riding over 3,300 miles in the past 11 days, meeting great people who love BMW bikes and especially the RS and attending a fabulous rally celebrating the 40th anniversary of the introduction of the R100RS.

Starting Mileage

Ending Mileage – Over 3,300 Miles

To all the airheads at the rally who directly helped me get there or took a moment to talk with me and provide words of encouragement that lifted my spirits, thank you from the bottom of my heart. RS riders in particular, and Airheads in general, are some of the nicest folks you could ever want to spend a weekend with.